An urban rail train bogie system is an important part of an urban rail train, which is used for transferring various loads, and utilizing an adhesion force between wheel rails to guarantee the generation of a traction force. To a great extent, the performance of the bogie system decides running stability and safety of the train. Therefore, it means a lot to the running stability and safety of the urban rail train how to accurately evaluate a reliability of the urban rail train bogie system and to predict a failure rate of the bogie system. Meanwhile, during the normal usage, the bogie system requests timely inspection, repair, and maintenance. What's more, the cost spent on inspection, repair, and maintenance of the bogie system takes a main part in the overall maintenance cost of the urban rail train. Therefore, the process of accurately evaluating a running status of the urban rail train bogie system and working out a reasonable repair plan of the bogie system has a great meaning in guaranteeing the urban rail train to run safely and economically.
The method for researching system reliability mainly includes a statistical model method and a mechanism model method. The statistical model method mainly analyzes a probability distribution function of the system failure time, and obtains reliability indexes associated with the system, for example, a mean time between failures, failure rate, etc. The mechanism model method mainly performs reliability analysis on a structural mechanism of the system. Considering the research about maintenance decision-making modeling, the prior art comprehensively considers the effects on the service life of the system caused by factors of running conditions, load, and so on, conducts the maintenance modeling for rotating machinery, and obtains better effects, which implies that the concomitant variable plays an important role in researching the service life distribution regularity of the system.
The above researches have made certain achievements in terms of both reliability analysis and condition-based repair of the bogie system. However, there are still some problems. (1) Currently, the above researches are mainly directed to railway passenger cars and railway freight cars, whereas the researches about the reliability of the urban rail train bogie are seldom performed. (2) The above methods are based on monitoring or inspection data, which sometimes cannot accurately master a service life of the bogie. Thus, it lacks of consideration about the time uncertainty. (3) In terms of the traditional mathematical description of system service life or system performance degradation, it is generally evaluated based on one-dimensional time variable. However, for a complicated system such as a bogie, due to the factors such as ambiguity of repair thresholds and randomness of failure mode, only one-dimensional time variable is not sufficient for making evaluations objectively. Instead, the effects on the system running caused by relevant concomitant variables such as performance parameter, failure type, and so on must be considered at the same time, and thus offering more powerful reference for making repair optimization decisions.